The vegetative and the minimally conscious state: brain function, connectivity and structural abnormalities

Departament/Institut:Universitat de Barcelona. Departament de Psiquiatria i Psicobiologia Clínica

Data de defensa:10-12-2010

Dipòsit Legal:B.10497-2011

ISBN:9788469406762

Paraules clau:Estat de mínima consciència (EMC);
Estat vegetatiu (EV)

Matèries:616.89 - Psiquiatria. Psicopatologia

Àrea de coneixement:Ciències de la Salut

Resum:

The Vegetative State (VS) is a clinical condition characterized by wakefulness in the absence of awareness of self or environment. A person in a VS retains autonomic functions but exhibits no evidence of voluntary responses to stimulation nor evidence of language comprehension or expression. Some VS patients may evolve to a Minimally Conscious State (MCS), demonstrating inconsistent but reproducible evidence of awareness. The differential diagnosis between these two conditions, as well as between them and other disorders such as coma or locked-in syndrome, is challenging and prone to errors. Neuroimaging techniques can shed light on this process by providing complementary information that cannot be obtained from a bedside examination. Using functional magnetic resonance imaging (fMRI) several authors have demonstrated that some VS and MCS patients may retain residual cognitive functions. However, to date, no functional or structural neuroimaging study has identified clear biomarkers that allow for differentiation between these two groups of patients.The present doctoral thesis consists of four studies with the general aim to examine the neuroanatomical and neurofunctional bases of the impairment of consciousness in VS and MCS patients. Firstly, we focused on the assessment of brain responses to speech in a group of VS and MCS patients by means of fMRI. Secondly, we combined fMRI, diffusion tensor imaging (DTI) and clinical and neuropsychological assessment to study the cerebral and clinical changes of a VS patient from the time of VS through to recovery. Finally, we applied DTI and high-resolution T1-weighted structural MRI to in-vivo characterize the neuropathological patterns of VS and MCS patients and explore possible differences between these two groups of patients. In the third study we focused on the subcortical white matter, brainstem and thalami, following post-mortem works. Based on the results obtained in that study, in the fourth study we focused on the thalamus and its global and regional atrophy.Taken as a whole the four studies included in this thesis contribute to a better characterization of the cerebral mechanisms that construct awareness and the structural and functional bases of the DOC. They further support the use of fMRI to detect residual cognitive function that may remain unobservable in bedside examinations of these patients. They also highlight the potential of the combination of structural and functional neuroimaging techniques in their study as well as their possible future use in the estimation of outcome. Furthermore, our results provide for the first time evidence that VS and MCS patients can be reliably distinguished in vivo in base of structural measures, suggesting that MRI techniques could be combined with other measures in the clinical field to help in the solution to the problem of misdiagnosis.